The third, and most complete, quote came from Gavin Schmidt, a climate modeler at the Goddard Institute for Space Studies, who said:
It is a truism to say that everything has been affected by climate change so far and therefore this latest outbreak must in some sense have been affected, but attribution is hard, and the further down the chain the causality is supposed to go, the harder this is. For heat waves it is easier, for statistics on precipitation intensity it is easier — there are multiple levels of good modeling, theory, and observations to back it up. But we have much less to go on with tornadoes.
Andrew Revkin put it a little more bluntly at his New York Times Dot Earth blog:
There’s no doubt that Michael Mann of Pennsylvania State University is right when he says “climate change is present in every single meteorological event” — in the sense that the buildup of greenhouses gases is a background nudge everywhere.
But that’s a meaningless assertion without asking whether there is evidence of a meaningful influence — meaning enough of a nudge to the atmosphere that the contribution from greenhouse gases is relevant to policy and personal choices, in this case in tornado zones.
Most major news outlets have done a good, stressing the immediate meteorological causes of the tornadoes and the high level of uncertainty surrounding their relation to climate change. Take the Q&A-style explainers published May 25 in the The New York Times and Los Angeles Times on pages sixteen and seventeen of the papers’ A sections, respectively. Take wire services like the Associated Press and Agence France-Presse, or magazines like Time. Take regional outlets like The Christian Science Monitor, the Houston Chronicle, the Kansas City Star, the Toledo Blade in Ohio, and the Anniston Star in Alabama. Take specialty publications like ClimateWire, LiveScience.com, and New Scientist.
One could pick nits with all of these pieces, but they faithfully and carefully convey the message of a preliminary report on April’s tornadoes from the National Oceanic and Atmospheric Administration’s (NOAA) Climate Attribution Rapid Response Team:
A change in the mean climate properties that are believed to be particularly relevant to major destructive tornado events has thus not been detected for April, at least during the last 30 years. So far, we have not been able to link any of the major causes of the tornado outbreak to global warming. Barring a detection of change, a claim of attribution (to human impacts) is thus problematic, although it does not exclude that a future change in such environmental conditions may occur as anthropogenic greenhouse gas forcing increases.
Some pieces didn’t display enough skepticism. A USA Today post, titled “Climate change could spawn more tornadoes,” is one example. It cited studies in Proceedings of the National Academy of Sciences and Geophysical Research Letters to support the headline’s assertion. Those papers focused on severe thunderstorms, which can create tornadoes and are likely to be more frequent in a warming world, but they didn’t actually say much about twisters themselves (which are not inevitable byproducts of severe thunderstorms).
After it was published in 2007, the author of the paper in Geophysical Research Letters, Anthony Del Genio, told the AP’s Seth Borenstein that “The strongest thunderstorms, the strongest severe storms and tornadoes are likely to happen more often and be stronger.” But last year he told the Toledo Blade’s Tom Henry that, “while scientists are convinced the status quo will result in more violent weather years from now, tornadoes are ‘really beyond the edge of our understanding of things.’” In 2008, a paper in Transactions of the American Geophysical Union emphasized that the relationship between tornadoes and climate change remained “mostly unexplored.” So did one in 2009 in Geophysical Research Letters.
Describing “the existing state of knowledge on climate change and tornadoes,” NOAA’s Climate Attribution Rapid Response Team cited the Intergovernmental Panel on Climate Change and the U.S. Climate Change Science Program, both of which agree that there is insufficient evidence to determine trends in the frequency and intensity of small-scale weather events like tornadoes. Indeed, there is a lot of evidence tempering USA Today’s declaration that “Climate change could spawn more tornadoes,” but its post mentioned none of it.
At any rate, McKibben’s contention that no one is “making connections” or asking questions about twisters and warming is completely unfounded. On May 5, NOAA’s own ClimateWatch Magazine reported, “These days, when the weather breaks records, it’s natural to wonder if global warming is to blame. So it’s not surprising that in recent weeks, climate scientists have been fielding lots of questions about the possible connection between global warming and tornadoes.”